For feminine countries (la France, l'Australie) you use "en". You don't use an article with "en".
For masculine countries starting with a vowel (l'Équateur, l'Uruguay) you use "en" as well.
For masculine countries starting with a consonant (le Canada, le Portugal) you use "au" which already includes the article.
For plural countries (les États-Unis, les Pays-Bas) you use "aux" which also includes the article.
In English, collective noun can often be treated as either singular or plural, depending on the usage or mindset. For instance, if the family all lives together, we may treat the members as a single unit; on the other hand, if they consider themselves a family group but maintain separate households or are known in separate contexts, we may treat them as multiple individuals. It appears that collective nouns are handled similarly in French.